MANILA (Reuters) - Philippine President Rodrigo Duterte’s critics and allies in the Senate vowed on Wednesday to block a lower house move to slash the annual budget of a public-funded human rights agency opposed to his bloody war on drugs to just $20.

The house, dominated by Duterte’s supporters, voted on Tuesday to allocate a 2018 budget of just 1,000 pesos ($20) to the Commission on Human Rights (CHR), which has investigated hundreds of killings during the president’s ferocious anti-narcotics crackdown.

Vice President Leni Robredo, who was not Duterte’s running mate and has locked horns with him numerous times, said the lawmakers’ move effectively abolishes the CHR, a constitutional body.

Duterte’s signature campaign has left thousands of mostly urban poor Filipinos dead. Critics say the lawmakers are trying to retaliate against the CHR for pursuing allegations of executions by police during sting operations, which police deny.

The CHR is among the domestic and foreign rights groups that Duterte frequently admonishes, accusing them of lecturing him and disregarding Filipinos who are victims of crimes stemming from drug addiction.

The upper house minority bloc, composed of six staunch critics of the president, will seek to restore the 678 million peso budget the government and a Senate sub-committee had proposed for the CHR.

Senator Risa Hontiveros described the plan to cut the budget to almost nil as “a shameless rejection of the country’s international and national commitments to champion human rights”.

Several allies of Duterte in the 24-seat chamber said they would scrutinize the house move and try to ensure the commission had a budget that would allow it to work properly.

FILE PHOTO: Philippine President Rodrigo Duterte gestures as he delivers his speech, during the oath taking of Philippine National Police (PNP) star rank officers, at the Malacanang Presidential Palace in Manila, Philippines August 30, 2017. REUTERS/Romeo Ranoco

Senator Richard Gordon said the CHR had a job to do and should not be restricted.

“That is their role - to expose possible abuses,” he said.

FILE PHOTO: Relatives and loved ones of Leover Miranda, 39, a drug-related killings victim, hold a streamer calling to stop the continuing rise of killings due to the President Rodrigo Duterte's ruthless war on drugs, during a funeral march at the north cemetery in metro Manila, Philippines August 20, 2017. REUTERS/Romeo Ranoco

Another legislator, JV Ejercito said senators would not make the CHR impotent.

“The CHR is in the thick of things and very relevant nowadays and probably even next year and the years to follow because of what’s happening,” he said in a statement.

Duterte once threatened to abolish the CHR after its chief, Chito Gascon, sought to investigate alleged abuses by police anti-drugs units.

Duterte on Tuesday appeared to distance himself from the lawmakers proposing the meager budget. He said CHR was constitutionally created and should probe whatever it wants, adding he was “not here to destroy institutions”.

“He had it coming. He opens his mouth in a most inappropriate way. He knows nothing,” Duterte said, referring to Gascon.

“The congressmen are really angry. I have nothing against him. Give them a budget for all I care, whatever he likes to investigate.”